Global Warming Makes Poison Ivy Itchier, More Ample, Study Says

WASHINGTON – Another reason to worry about global warming: more and itchier poison ivy. The noxious vine grows faster and bigger as carbon dioxide levels in the atmosphere rise, researchers report Monday.

And a CO2-driven vine also produces more of its rash-causing chemical, urushiol, conclude experiments conducted in a forest at Duke University where scientists increased carbon-dioxide levels to those expected in 2050.

Carbon dioxide is a greenhouse gas — a chemical that traps heat similar to the way a greenhouse does — that's considered a major contributor to global warming. Greenhouse gases have been steadily increasing in the atmosphere since the Industrial Revolution.

Poison ivy is common in woods around the country, making it a bane of hikers, campers, fighters of forest fires, even backyard gardeners. Its itchy, sometimes blistering rash is one of the most widely reported ailments to poison-control centers, with more than 350,000 reported cases a year.

Compared to poison ivy grown in usual atmospheric conditions, those exposed to the extra-high carbon dioxide grew about three times larger — and produced more allergenic form of urushiol, scientists from Duke and Harvard University reported.

"The fertilization effect of rising CO2 on poison ivy ... and the shift toward a more allergenic form of urushiol have important implications for the future health of both humans and forests," the study concludes.